1. Field of the Invention
The present invention relates in general terms to a propulsion assembly for an aircraft, of the type comprising a jet engine, a nacelle enclosing the jet engine, and an attachment strut provided with a rigid structure and means of attaching the jet engine to the rigid structure.
More precisely, the invention relates to an intermediate casing extension for the jet engine in such an assembly, intended to produce the interface between the intermediate casing and thrust reverser covers of the nacelle.
2. Description of the Related Art
The attachment strut, also referred to as an EMS (from the English Engine Mounting Structure), or pylori, or engine pylori, makes it possible to suspend the jet engine below the aircraft wing, or to mount this jet engine above this same wing, or to attach it at the rear part of the fuselage. It is in fact provided to form the connection interface between a jet engine and a given structural part of the aircraft. It makes it possible to transmit to the structure of this aircraft the forces generated by its associated jet engine and also allows the routing of the fuel, electrical and hydraulic systems and air between the engine and the aircraft.
The nacelle for its part is conventionally equipped with several covers enclosing the jet engine and allowing access to the latter in the open position, these covers being known by the terms fan covers and thrust reverser covers, the latter being articulated on the primary structure of the attachment strut.
The jet engine comprises a fan casing extended towards the rear by a so-called intermediate casing, comprising an external shell and a front transverse plate and a rear transverse plate parallel and disposed radially internally with respect to this external shell, this intermediate casing also comprising structural arms distributed angularly and extending radially between the front and rear plates, as far as the external shell.
It is this same external intermediate casing shell that is extended downstream by an extension comprising an annular connecting downstream end forming an annular groove open radially towards the outside, intended to receive the nacelle covers, and more precisely a rib of complementary shape carried by these same covers, generally the thrust reverser covers. Thus the cooperation between the rib and the complementary groove allows the transmission of the aerodynamic forces from the nacelle to the jet engine, in takeoff, flight and landing phases, in particular the axial forces, and even more particularly the counter-thrust axial forces when the thrust reverser systems equipping the nacelle covers are actuated.
In addition, the simple penetration of the rib into the groove provides easy and rapid opening of the reverser covers articulated on the strut, this opening being for example produced for implementation of maintenance operations on the aircraft parked on the ground.
One drawback relating to this solution lies in the fact that the annular groove, continuous or interrupted along the circumference of the extension, is produced within one and the same annular piece, which it is necessary to change fully in the event of damage to part of the groove receiving the covers. This drawback is extremely detrimental, especially as it has been found that the annular groove is generally stressed by the covers disproportionately along it, involving the appearance of very localised wear zones.